Olopatadine is an antihistaminic drug, used for the treatment of ocular symptoms of seasonal allergic conjunctivitis. Olopatadine was developed by Kyowa Hakko Kirin Co. Ltd. and produced commercially by the synthetic route using Wittig reaction as key step. Although both olopatadine Z and E isomers show similar H1R affinities, only the Z isomer is the marketed drug. Because of antiallergic activity many chemists are involved developing a better process for Z-isomer of olopatadine (FIG. 1).
